Using Design Patterns In Real Projects

Using Design Patterns in Real Projects -Andy Bulka 2002 http://www.andypatterns.com

Using Patterns in Real Projects • What is it like to use design pattern in real life programming? • Do the sometimes academic patterns translate into the real world? • The answer is yes – I will back this up with three examples of where I have used patterns in real world projects.

Overview • Patterns - Definitions • Patterns Example • My personal definition and approach to patterns • Commercial Projects using patterns • Patterns I have written • Links, Patterns Groups in Australia

What are Patterns? • Patterns are conventions for describing and documenting recurring design decisions within a given context, in software design & engineering. • A problem/solution pair given a standard name. • A pattern is documented using a standard format which includes a sample UML diagram of a typical solution.

Example - Adapter Pattern

• Convert the interface of a class into another interface clients expect. • Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.

Adapter - two solutions Adapter comes in two variants; one making use of delegation:

and one based on multiple inheritance

Design Patterns Book The "Bible" of Design Patterns

Pattern Format • • • • • • •

Pattern templates typically contain: Name Intent / Motivation Problem Context & Forces Solution Consequences

To Record Experience...

Anecdote - working alone...

To Share Experience...

Personally I think Patterns are • Share and document experience • Great as a vocabulary between programmers and design tool • Like problem / solution pairs • Just a name for a new „thick/non-obvious‟ concept? A „distinction‟. • Later patterns become common terms.

Commercial Projects Educational Reasoning Software Payroll System War Game

Reason 2 - Melb University • • • •

Mentor in Delphi & OO Patterns where possible Model - „cauldron of creation‟. Composite. Command, Template, Strategy for persistence, Adaptor incl. delegation via a pointer “this is an important idiom” • Model View Controller variation MGM. Hooking up a standard Windows GUI treeview to model.

Reason 2 - UML There are several design patterns in this UML diagram. P.S. In later years I became interested in how to explicitly represent patterns in UML diagrams..

Reason!Able www.goreason.com

Game - 2D wargame • • • • • •

Python SDL graphics (pyGame) Single and Multiplayer over internet Game AI Lots of pieces Moving Scrolling map

Game - Preparation • Starting a new project in a new domain - I wanted to know what best practices were. • “Game patterns” on the web documented best practices, tips and tricks and useful rules of thumb and mini designs. • Melb Patterns Group presentation • Patterns used so far - MVC, Façade, Singleton, MGM, Mediator, RM, TI, Null Object, Adaptor, Strategy, Observer, State.

Game Patterns as UML

Game so far

Game Gems & AI Wisdom book • Patterns vs. “Gems” • Patterns vs. “Problem / Solution pairs” • Still talk about forces and consequences and trade-offs, though not as formal section headings. • Some sections not strictly suited to being a pattern, instead they talk about optimisations or more specific issues.

Payroll System • Delphi project • Experienced content expert • Was a payroll patterns paper at KoalaPlop 2002 • See also “Business Modelling in UML” by Eriksson & Penker - “Business Patterns at Work”. • Transformation Interface Pattern (Gui and DB versions)

Australian Patterns Conference

Venue The Country Place Conference Centre Location: The Dandenongs International visitors

Patterns I have written for the conference • Model Gui Mediator • Relationship Manager • Transformation Interface

See www.andypatterns.com

Plop Conference Proceedings

Links • KoalaPLoP is hosted in Melbourne http://www.mcs.vuw.ac.nz/~kplop

• Melbourne Patterns Group http://www.melbournepatterns.org